Volumetric Replacement Research Articles

Effect of accelerated carbonation on fine cement paste aggregates

Accelerated carbonation is suggested as a potential alternative for carbon dioxide sequestration, which also improves the microstructure of recycled concrete aggregates. In this study, the carbonation parameters of model aggregates derived from cement pastes with two different water/cement ratios (i.e., 0.5 and 0.7) were evaluated in order to maximize the benefits of the carbonation process on their density and absorption. For this purpose, in a first phase, the initial moisture content of the model aggregates and the reaction time were evaluated. Furthermore, in a second phase of mortar production, the fraction of fine natural aggregates was replaced, considering each type of unprocessed and carbonated model aggregate at volumetric replacement percentages of 50% and 100%, varying the amount of water in the mortar mix to maintain a similar workability in all the series. In this way, the properties of the eight series of mortars are evaluated in comparison with the control series made only with natural aggregates. The results indicate that the accelerated carbonation process positively influences density and absorption in the model aggregate. Regarding the parameters of the accelerated carbonation environment analyzed, for a higher w/c ratio in the original model aggregate, higher initial water content was necessary for the carbonation process to be efficient. As for the mechanical performance of the mortars with model aggregate, the series that incorporated model aggregate aggregates with a w/c ratio of 0.5 achieved better mechanical behavior compared to the series replacing model aggregate with a w/c ratio of 0.7; this was related to the formation of a more compact matrix in the mortar with model aggregate of cementitious pastes.

Internal Curing Utilising Recycled Concrete Aggregate: A Sustainable Approach for Improving High-Strength Concrete’s Performance

AbstractHigh-strength concrete (HSC) makes up the vast majority of materials used in the construction sector due to its exceptional mechanical characteristics and outstanding long-term behaviour. However, in cement-based materials with a low water-to-binder ratio (w/b), excessive autogenous shrinkage has become a prevalent issue. This work suggests the sustainable use of recycled concrete aggregate (RCA) to internally cure HSC in order to reduce autogenous shrinkage during the hydration and curing processes. RCA was employed with various volumetric replacement percentages with natural coarse aggregate as a water storage agent (0%, 8%, 16%, 24%, 32%, 50%, 75%, and 100%) under sealed and unsealed conditions. The efficiency of the adopted materials for internal curing was investigated by determining the autogenous shrinkage in addition to unconfined compressive and flexural strength. The laboratory results reveal that the studied properties significantly improved by incorporating RCA into HSC, and the improvement depends on the substitution rate of the coarse aggregate. A better shrinkage behaviour can be obtained by raising the substitution percentage of coarse aggregate with RCA; in contrast, the strengths decrease with increased RCA. RCA can be utilised as an internal curing material for HSC to alleviate autogenous shrinkage with a percentage of around 40%, with the adopted ambient conditions in the early age of HSC with full replacement of virgin coarse aggregate. It is recommended to use 24% RCA as a substitution for natural coarse aggregate for internal curing to improve the characteristics of HSC and the sustainability advantages and reduce its negative environmental impacts.

Experimental and numerical investigation of the bending, shear, and punching shear behavior of recycled aggregate concrete precast/prestressed hollow core slabs

AbstractAlthough it has been shown that using recycled concrete aggregate in new structural concrete is economical and sustainable, the use of this material for such applications is still not widespread. One of the reasons is that manufacturers, designers, engineers, owners, and other market players are not familiar with specifying and utilizing this material—although standards are starting to incorporate provisions for recycled aggregate concrete, successful, practical example projects are needed. The current paper describes the results of a partnership between universities and a precast concrete manufacturer of hollow core slabs. Seven hollow core slabs with volumetric replacement ratios of natural aggregate with recycled aggregate from 0% to 60% were tested to failure in both bending and shear, and then undamaged portions of the slabs were subjected to punching shear until failure. The results showed only mild differences in strength, with different replacement percentages of recycled aggregate under the various loading scenarios. Numerical simulations performed in Abaqus demonstrated the feasibility of analyzing recycled aggregate concrete structural elements and provided important insights into their behavior.

Effect of waste tire products on some characteristics of roller-compacted concrete

Abstract Roller-compacted concrete pavement (RCCP) is one of the most durable, economical, and practical solutions for the construction of roads for various heavy-duty purposes. To make RCCP more sustainable, different waste materials have been utilized. These materials were densified silica fume (SF), ground granulated blast furnace slag (S), crumb rubber (CR), and recycled steel fibers (RSFs) from waste tires. The weight percentages of replacement for SF and S from cement were 5, and 27.5%, respectively. CR was utilized as a volumetric replacement of sand with 0, 2, 5, and 10%. As a volumetric addition of concrete, RSF with 0.2, 0.4, and 0.6% was utilized. Water content was 6% for all mixtures. The impact resistance test was performed to evaluate the behavior of RCCP to the repeated load on roads. Also, ultrasonic pulse velocity (UPV) (nondestructive) and abrasion resistance tests were performed to validate roller-compacted concrete (RCC) as pavement. There is a substantial increase in impact energy by using 10% of CR and 0.6% of RSF, compared with that of reference specimens. The use of CR and RSF can improve the abrasion resistance of RCC, and this can ensure its applications in pavements. The relationships between impact, abrasion, and UPV were established, and models have been proposed to predict these relationships.

Experimental investigation on the freeze-thaw durability of a phase change concrete in cold regions

In cold regions, freeze-thaw induced damage to concrete is among the most severe issues that affect structures, leading to shortened lifespans of concrete-related structures and causing substantial economic losses. Therefore, it is crucial to enhance the freeze-thaw durability in cold regions. To achieve this aim, we combined n-tetradecane (C14) and expanded perlite (EP) to produce a composite phase change material (EPC14) with cement encapsulation. The essential material performances of the EPC14 were characterized through a series of physical and chemical tests. The measurement results show that the EPC14 possesses an appropriate phase change temperature, chemical stability, and mechanical reliability. Hence, it is an excellent candidate material for producing phase change concrete. In this study, we selected five volumetric replacement ratios of the EPC14 to fine aggregates (0%, 10%, 20%, 30%, and 40%) to prepare the phase change concretes (PCC-EPC14s). After these PCC-EPC14s samples were properly cured and then underwent 0, 50, 100, and 200 freeze-thaw cycles (FTCs), their physical and mechanical properties were systematically measured through nuclear magnetic resonance (NMR), resonance frequency tests, and uniaxial compression tests. The comprehensive measurement results demonstrate that at 0 FTCs, a higher content of the EPC14 results in larger porosity in the PCC-EPC14s, leading to lower compressive strength and relative dynamic modulus of elasticity. However, after 200 FTCs, the PCC-EPC14 (20%) exhibits the highest compressive strength and relative dynamic modulus of elasticity, whereas the PCC-EPC14 (0%) exhibits the lowest values for both of these properties. Furthermore, fractal theory was employed to analyze the mechanical properties of the PCC-EPC14s from a microscopic perspective. The results indicate that the PCC-EPC14 (20%) exhibits the largest NMR fractal dimension after 200 FTCs, signifying the least complexity and integration in its pore structure. In comparison to the PCC-EPC14s (0%, 10%, 30%, 40%), it is less prone to developing damage cracks under compression. In conclusion, we advise using the PCC-EPC14 (20%) in practical construction projects. The PCC-EPC14s prepared in this paper offer valuable insights for enhancing the freeze-thaw durability of concrete in cold regions.

Compressive behaviour of FRP-confined rubberised alkali-activated concrete

This paper presents experimental and numerical assessments into the compressive stress-strain behaviour of circular FRP-confined rubberised alkali-activated concrete with unidirectional sheets incorporating fibres in the hoop direction. The parameters investigated in the experimental programme include three different rubber contents of 0%, 30% and 60% volumetric replacement of the total natural aggregates and three confinement levels of 1–3 aramid FRP layers. The numerical assessment is performed in ABAQUS/CAE and a new strain hardening-softening function is developed for the compressive behaviour in the Concrete Damaged Plasticity material model, which captures the passive confinement imparted by the FRP jacket on the rubberised concrete. The numerical results are validated against the experimental results and a parametric study involving 240 models covering a wide range of parameters, including varying FRP materials (basalt, glass, aramid, and carbon), reference concrete grades, rubber replacement ratios, and confinement levels, is performed. The experimental results show an increase in the confinement effectiveness, i.e., confined-to-unconfined strength, by 66.7% and 103.4% for specimens with 0% and 60% crumb rubber replacement ratio, respectively, as the number of FRP layers increase from 1 to 3. Test specimens with 0% and 60% crumb rubber replacement ratio indicate an increase in the ultimate axial strain by 228.2% and 76.2%, respectively, as the number of FRP layers increase from 1 to 3. The observed hoop rupture strain reduces by 32.8% and 21.3% for specimens with 0% and 60% crumb rubber replacement ratio as the number of FRP layers increase from 1 to 3, showing a trend of reduction in the hoop rupture strain with higher FRP confinement layers and rubber content. The numerical results show that the enhancement in compressive strength is linearly proportional to the confinement ratio and is only marginally influenced by the FRP jacket stiffness at a given confinement ratio. The ultimate axial strain enhancement is also linearly proportional to the confinement ratio but is dependent on the FRP jacket stiffness. The compressive stress-strain curve for sufficiently confined specimens is also shown to be well represented by a bi-linear curve with hardening. Based on the findings, a design-oriented model is introduced for sufficiently confined specimens and is shown to be in close agreement with the experimental results.

Flexural behavior of steel fiber reinforced concrete beams comprising coarse and fine rubber and strengthened by CFRP sheets

Despite having many advantages, using rubber to produce reinforced concrete members like beams is still restricted. When there is more waste tire rubber in concrete structures, rubber concrete's flexural and compressive strengths gradually decrease. However, this study used steel fibers to improve compressive strength and externally bonded carbon fiber-reinforced polymer (CFRP) sheets to increase flexural strength. Four groups of three reinforced concrete beams each were established for the study's use. The first and third groups of concrete beams used a volumetric replacement of fine and coarse aggregates with 5% and 10% waste tire rubber. However, steel fibers were added to the second and third groups at a rate of 1.25% of the concrete volume. Waste tire rubber and steel fibers were not replaced or added to the fourth group, the main reference group. The dimensions of each beam were 2.1×0.2×0.3 m. A concrete beam's first member is always free of external reinforcement, followed by its second member, which has one layer, and its third member, which has two layers of CFRP sheet. ABAQUS, a finite element analysis program, was used numerically to represent the third strengthening layer. The results showed that strengthening the reinforced rubberized concrete beams with a single layer of CFRP sheets increased the load at first crack and failure by 8.57% and 17.64%, respectively, compared to the unreinforced reference beam, compensating for the loss caused by the production of rubberized concrete and adding additional flexural strength. These loads increased by 31.43% and 26.45%, respectively, due to the steel fibers added to the beams containing these waste tire rubber. Strengthening with two layers of CFRP sheets increased the load at first crack and failure by 17.14 and 34.27, respectively. The steel fibers added to the beams that contained these amounts of waste tire rubber, on the other hand, caused these loads to increase by 42.86 and 49.23%, respectively. Strengthening with three layers numerically results in an exponential increase in load at the first crack and the failure by 8.03 and 52.88%, respectively. On the other hand, the loads on the beams that contained these quantities of waste tire rubber increased by 50.49% and 104.47%, respectively, when steel fibers were added to them.

Rheology of self-compacting concrete containing silica fume and recycled aggregates

Rheology of Self-Compacting Concrete (SCC) containing selected silica fume dosages (0% (control mix), 5%, 10% and 15%) in a binary binder has been investigated using the flow-curve test protocol implemented on a co-axial cylinder rheometer. At each silica fume dosage, coarse recycled concrete aggregate volumetric replacement levels were 0%, 50% and 100%. Calibration of selected flow models with the measured flow data showed that rheology transitioned from shear thickening to shear thinning as the silica fume dosage increased from 0% to 15%, other mix constituents remaining unchanged. Similar flow behaviour was noted in the SCCs made with the recycled concrete aggregates (SCRACs) across all replacement levels though for a given silica fume dosage, degree of shear thinning decreased with increasing contents of the coarse recycled aggregates. The experimental results have been used to propose a workability box containing bounds for acceptable rheology of the SCCs and the SCRACs.

Effect of lightweight expanded clay aggregate as partial replacement of coarse aggregate on the mechanical properties of fire-exposed concrete

Abstract As aggregate material typically comprises 65–75% of concrete volume and has a significant effect on its mechanical properties, aggregate type considerably affects concrete behavior at high temperatures. In this study, 80 concrete cylinders and 60 cubes were cast to investigate the residual strength of normal concrete that contains lightweight expanded clay aggregate (LECA) with different volumetric replacement ratios (0, 10, 20, and 30%) of the coarse aggregate. After the fire flame exposure effect of steady-state temperatures (300, 400, 500, and 600°C), and a sudden cooling process, the mechanical tests (compressive strength, tensile strength, and modulus of elasticity; Ec), as well as mass loss and thermal conductivity, were carried out on the specimens. The results indicate that increasing the LECA content in the mixture leads to better strength retention after exposure to fire. After exposure to a steady-state temperature of 600°C, the amount of decrease in mass, residual compressive and tensile strengths, and the residual amount of Ec were 7.61, 7.5, 7.16, and 6.24%; 57.1, 66.8, 69.8, and 72.0%; 22.4, 32.7, 41.8, and 48.6%;, and 16.0, 22.3, 23.4, and 24.3%, respectively, for the considered volumetric replacement ratios of 0, 10, 20, and 30%. Also, the values of the thermal conductivity were 1.4889, 1.1667, 1.0912, and 1.0410 W/m K, respectively.

Inspection of Thermo-Mechanical Behavior on Sintered Fly Ash Aggregate in Pavement Quality Concrete

Conventional concrete pavement is more efficient towards mechanical load but combing with environmental loads compromises serviceability. This paper mainly focuses on utilizing sintered fly ash (SFA) aggregate to partially replace coarse aggregate in pavement quality concrete. Incorporating SFA aggregate in concrete pavement enhances the thermal behavior of rigid pavement due to higher voids and lower thermal conductivity. Coarse aggregate was partially replaced with SFA aggregate at an interval of 10 % till 40% by volumetric replacement. Pavement quality concrete (PQC) was designed as per Indian standards with a fixed water-cement ratio of 0.36 to achieve a minimum of 40 N/mm2 compressive strength. Compressive, split tensile and flexural strengths were inspected as mechanical behavior and thermal conductivity was examine as thermal behavior of different SFA mixed PQC. It has been observed that there is a slight decrement in mechanical strength by incorporating SFA in PQC but the thermal property of PQC was improved. Overall, it can be concluded that incorporating SFA at a certain level enhances the combined thermo-mechanical properties of PQC.

Assessing the Effect of Using Porcelanite on Compressive Strength of Roller Compacted Concrete

Roller-Compacted Concrete (RCC) is a zero-slump concrete, with no forms, no reinforcing steel, no finishing and is wet enough to support compaction by vibratory rollers. Because the effectiveness of curing on properties and durability, the primary scope of this research is to study the effect of various curing methods (air curing, emulsified asphalt(flan coat) curing, 7 days water curing and permanent water curing) and different porcelanite (local material used as an Internal Curing agent) replacement percentages (volumetric replacement) of fine aggregate on some properties of RCC and to explore the possibility of introducing more practical RCC for road pavement with minimum requirement of curing. Cubes specimens were sawed from the slabs of (38*38*10) cm for determination of compressive strength. The results show that using (5) % porcelanite improved the compressive strength of RCC (with air curing) as compared with reference RCC (with permanent curing) by percentage ranging from(-2.9 to 6)%.

Development of sustainable concrete using recycled polyethylene terephthalate (PET) granules as fine aggregate

Solid waste management has become a significant environmental challenge globally. This study aims to examine the performance of sustainable concrete incorporating polyethylene terephthalate (PET) granules as partial (0%, 10%, 30%, and 50%) volumetric replacement of sand. The mechanical properties including compressive strength, tensile strength and elastic modulus were examined. The flexural and cracking performance of the reinforced concrete (RC) beams, as well as bond behaviour of concrete mixes with steel reinforcement were investigated. Incorporating 10% PET granules demonstrated positive impact on the mechanical properties, flexural strength and cracking behaviour of RC beam, as well as bond strength. A theoretical model was proposed for predicting bond strength of concrete containing PET granules and the results corresponded well with both experimental and previous research findings. The American and Australian standards conservatively predicted cracking and flexural moments of the RC beams. Finite element modelling was conducted on the RC beams and the results corresponded well with the experimental findings.

Utilization of plastic waste as replacement of natural aggregates in sustainable concrete: effects on mechanical and durability properties.

The study presents the mechanical and durability properties of concrete made up of recycled-waste-polyethylene (PE) and waste-polyethylene-terephthalate (PET)-based aggregate as replacement of natural fine and coarse aggregate, respectively. For this purpose, compressive strength, sorptivity, water permeability, aggressive exposure in acid, base, marine and wastewater, impact resistance, abrasion loss including surface and Cantabro, gas permeability, rapid chloride penetration test (RCPT), elevated temperature and leachability test of microplastic were performed. The experimental works were performed for different volumetric replacement (0-40%) of natural fine and coarse aggregates by PE and PET made aggregate respectively for different curing periods. The experimental results revealed that the sorptivity of PE-based concrete was lowest. Water permeability coefficient signified that with the increase of percentage of PET water permeability increased. In case of aggressive exposure test, the percentage of residual mass and residual strength for all replacement was decreased with the increase in exposure period. Further, impact resistance test result signified that energy absorption increased with the increase of PE and PET percentages. Cantabro and surface abrasion weight loss showed similar trend. Carbonation depth was increased with increasing percentages of PE and PET signified strength decreased with increase of percentages of PE and PET when subjected in CO2. RCPT test results demonstrated that with increase of PE and PET percentages chloride ion penetrability was reducing. It is observed that below 100°C temperature, compressive strength of all mix proportions was not affected with elevated temperature. Moreover, the PET-based concrete showed no presence of microplastic in case of leachability test.

Compressive and splitting tensile impact properties of rubberised one-part alkali-activated concrete

This paper presents an experimental assessment of the compressive and splitting tensile properties of rubberised one-part alkali-activated concrete under quasi-static and low-velocity impact loading. An optimised mix design, employing blast furnace slag and fly ash as precursors and anhydrous sodium metasilicate as a solid activator, is used as a reference. Rubber contents of up to 60% volumetric replacement of total natural aggregates are considered. Quasi-static tests are performed using servo-hydraulic machines, whilst the impact tests are performed in an instrumented drop-weight loading rig. Digital image correlation is used to get displacement measurements under both quasi-static and impact loading conditions. Three impact velocities of 5, 10, and 15 m/s are considered, giving rise to strain-rates in the range of 3–270 s−1. The quasi-static results show shape- and size-dependency and characteristically lower compressive and splitting tensile strengths with higher rubber content. The dynamic properties are notably influenced by the rubber content, with a higher ratio resulting in greater impact duration under compressive loading, reduced peak compressive strength, and reduced peak splitting tensile strength. The shape of the stress-strain response under compressive loading changes with rubber addition, showing two major peaks as opposed to a single peak for the non-rubberised specimens. The dynamic mechanical properties are also strain-rate dependent, exhibiting an increase with higher strain-rates. The rubberised specimens exhibit higher strain-rate sensitivity in splitting tension than compression, signified by higher dynamic increase factors for a given strain-rate and lower critical transition strain-rates. A higher rubber content in the mix also result in reduced critical transition strain-rates for the compressive strength, axial crushing strain, and splitting tensile strength. Based on the results of this study, analytical expressions are provided for predicting the dynamic increase factors for the compressive strength, axial crushing strain, elastic modulus, and splitting tensile strength.

Mechanical engineering advantages of a dual fuel diesel engine powered by diesel and aqueous ammonia blends

With the assistance of Diesel-RK software, the volumetric replacement of aqueous ammonia (NH4OH) with original diesel is being investigated in a dual-fuel diesel engine. Three volumetric percentages of ammonia solution are used along with diesel according to the scenario: (40% NH4OH + 60% Diesel), (50% NH4OH + 50% diesel), and (60% NH4OH + 40% diesel). The numerical analysis is based on a multizone combustion model. In the zone-based approach, the governing equations for each zone are solved as open systems. Comparing diesel fuel with ammonia solutions, the results show that adding ammonia solutions decreases combustion pressure and heat release and increases Sauter diameter and ignition delay. Generally, the use of aqueous ammonia drops engine performance regardless of the percentage of NH4OH used. Since 40%, 50%, and 60% of NH4OH have lower heating values than diesel, BSFC is reduced by 7.15, 10.4%, and 15.38%, respectively. Since the addition of ammonia reduces combustion temperature significantly, a noticeable reduction in NOx emissions is achieved, reaching up to 61.75% in the case of 60% NH4OH. The results highlighted a remarkable reduction in soot emissions (43.4% for 40% NH4OH, 51.04% for 50% NH4OH, and 49% for 60% NH4OH) because the diesel was replaced with no carbon fuel, hence the engine produced less smoke compared to with the baseline case (pure diesel).

Packing density investigation of blended cement pastes incorporating waste perlite and recycled concrete powder

Widely available industrial local waste materials could be viable solutions as supplementary cementitious materials. Aside from their possible positive effect on material properties, benefits are also expected in the environmental and economic sense. This is the case mainly because these materials do not have value in the market and are discarded as waste. This research examines locally abundant waste powders from the production of recycled concrete aggregate and perlite. For the investigation, the wet packing density method was used based on volumetric replacement ratios of cement ranging from 2.5 to 12.5% and 2.5 to 7.5% for waste perlite and recycled concrete powder, respectively. The ternary blended cements showed beneficial behaviour when compared to reference containing solely ordinary Portland cement. On the other hand, compressive strength is one of the key indicators of porous materials' mechanical and durability performance. Compressive strength measurements for the blended cement pastes were also obtained to identify the possible enhancement in the packing density and its effect on the mechanical properties of cementitious materials. It has been demonstrated that focusing just on packing density for investigation of the mechanical performance of cementitious materials when alternative solutions are concerned might not be the most robust approach.

Study on green concrete replacing natural fine and coarse aggregate by plastic waste – An experimental and machine learning approach

One of the most universally used materials in construction industries is concrete because of its accessibility, affordability, extended lifespan and resistance to damage against unfavourable weather conditions. However, there is a massive depletion of valuable natural resources for the concrete production. Further, plastic consumption as well as waste generation is increasing day by day which is very much challenging to be managed as it is non-biodegradable and creates various environmental pollution. Thus, the usage of plastic waste as a fractional substitution of natural aggregates in construction industry may mitigate the problems. For the present study, nine concrete mixtures of M30 grade concrete containing recycled plastic waste polyethylene (RPE) and plastic waste polyethylene-terephthalate (WPET) were prepared as a fractional volumetric replacement for both natural coarse aggregates (NCA) and fine aggregates (NFA). The replacement levels were 0%, 5 %, 10%, 15%, 20%, 25%, 30%, 35% and 40% keeping constant the water-cement ratio (0.37).The usage of waste plastic aggregates for preparation of concrete were assessed through different fresh and hardened properties like slump, dry density, compressive strength (CS), flexural strength (FS), split tensile strength (STS) and ultrasonic pulse velocity. The test results corroborates that the slump increased with higher percentage replacement of waste plastic aggregate (PA) in concrete. Further, incorporation of WPET and RPE in concrete reduced the dry density by 10.59 % at 40% mix proportion. It is to be mentioned that, the CS decreases with with increase of partial replacement of natural aggregate with waste PA. The ultrasonic pulse velocity (UPV) also decreased with increase of the PA. The test result also depicted that up to 5% replacement the STS value is almost constant, after that it reduces. Further, in case of FS test, the replacement with waste PA concrete by 10%, the FS improved to 19.91%. Furthermore, the data prediction models of slump, CS, FS and STS were developed by artificial neural network. Moreover, the optimization of mix proportion was conducted by factor response optimizer with composite desirability of 0.65.

An experimental investigation of the optimum replacement ratio of coarse gravel with expanded polystyrene beads in concrete

Previous researches have shown that partial replacement of aggregates with Expanded Polystyrene (EPS) in concrete mixes reduces both the density and compressive strength of concrete, but enhances its durability. As there is no effort was made to determine the optimum EPS/gravel replacement ratio in a concrete mixture, this study triedl to determine this ratio. An experimental investigation is performed by using six different concrete mixes produced by partially replacing gravel with an equivalent volume of EPS beads. The adopted volumetric replacement ratios of coarse aggregate by EPS were (11%, 22%, 33%, 44%, and 55%). The results indicated that A drop in the density of both the fresh and hardened concrete was found to be in the range (of 0% to 35%) compared to the corresponding density value of the base mix (without EPS). Concrete compressive strength was also found to drop in the range (0% to 91%) compared with the corresponding value of the base mix. Within the limit of this work, it was found that the 22% replacement volumetric ratio of coarse aggregate with EPS is the optimum ratio based on a ratio of the drop in density to the drop in compressive strength. Generally, it was concluded that the optimum volumetric replacement ratio lies between 15% to 30%, according to the comparison with other prior studies.

ASSESSMENT OF SUSTAINABLE GREEN CONCRETE PROPERTIES USING RECYCLED PLASTIC WASTE AS REPLACEMENT FOR FINE AGGREGATE USING MACHINE LEARNING TECHNIQUE

The use of waste plastic as a replacement for natural aggregates in cement composites can solve the problem of the disposal of waste plastics sustainably. This study aims to investigate and compare the impact of replacing fine natural aggregate with recycled aggregates made up of polyethylene (PE) in M30 grade of concrete by analyzing the physical and mechanical properties of both fresh and hardened concrete in terms of workability, dry and fresh unit weight, 28-day compressive strength, flexural strength, split tensile strength, and ultrasonic pulse velocity. Nine concrete mixtures containing PE was prepared as a partial volumetric replacement for fine aggregate with substitution levels of 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35% and 40%. Due to the application of superplasticizers, the workability of concrete containing recycled plastic has improved. The fresh and dry unit weight values of the PE-based concrete decreased by 8.16% and 8.6%, respectively, with the increase in PE aggregate and can therefore be considered lightweight concrete. The compressive strength of concrete at various ages is reduced as the quantity of plastic in concrete increases. As the PE replacement ratio in concrete increased, the flexural strength and split tensile strength also declined. Up to 10% replacement gives acceptable physical and mechanical properties of concrete for structural purposes. In this study, artificial neural network (ANN) was used to predict the fresh and hardened properties of waste plastic aggregate-based concrete, and it was discovered that it can predict concrete qualities with good accuracy (R<sup>2</sup> = 0.99).

The influence of anhydrite III as cement replacement material in production of lightweight masonry blocks for unreinforced non-load bearing walls

Lightweight cellular hollow concrete (LCHC) block is a type of masonry unit that has excellent thermal and acoustic performance, fire resistance and high weathering resistance, and manufactured by precast technique. This work presents an experimental study, which investigates the effects of volumetric partial replacement of Portland cement by calcium sulfate anhydrite on precast properties, especially hardening time of the products, thermal insulation properties and mechanical properties of the blocks. LCHC block is produced by the mixing of Portland cement (PC), anhydrite III (ANH), expanded perlite (EP), pumice (PU) and calcite (CA) for building applications. The physical and mechanical properties of LCHC blocks having various replacement levels of ANH are studied. Experimental studies were carried out on both 10x10x10 cm3 cube specimens and 19x19x39 cm3 block specimens. In this research work, LCHC blocks with 16 different mixture batches were cast into a mould with vibro-compacting, de-moulded immediately and transferred to a storage area for curing up to 28 days in normal air condition. The unit weights and compressive strengths of the cube specimens decreased as the ANH replacement level increased, depending on the decrease in the cement ratio. However, it was observed that the compressive strength of the block specimens increased up to the volumetric replacement level of 1.86 %. As expected, the thermal conductivity values of the specimens decreased with the decrease in unit weight. The most notable change on the specimens occurred in the hardening time. The hardening process of the specimens can be completed up to 90 times faster than the control mixture. In addition, within the scope of the study, three formulations are presented in which the compressive strength and the elastic modulus of the wall sections made with LCHC blocks can be calculated, and thermal conductivity value of masonry block unit can be calculated.